them is deficient,
_weakness_ is produced, as applied to the motions of animal bodies.

Now as the sensorial power, or spirit of animation, is perpetually
exhausted by the expenditure of it in fibrous contractions, and is
perpetually renewed by the secretion or production of it in the brain and
spinal marrow, the quantity of animal strength must be in a perpetual state
of fluctuation on this account; and if to this be added the unceasing
variation of all the four kinds of stimulus above described, which produce
the exertions of the sensorial powers, the ceaseless vicissitude of animal
strength becomes easily comprehended.

If the quantity of sensorial power remains the same, and the quantity of
stimulus be lessened, a weakness of the fibrous contractions ensues, which
may be denominated _debility from defect of stimulus_. If the quantity of
stimulus remains the same, and the quantity of sensorial power be lessened,
another kind of weakness ensues, which may be termed _debility from defect
of sensorial power_; the former of these is called by Dr. Brown, in his
Elements of Medicine, direct debility, and the latter indirect debility.
The coincidence of some parts of this work with correspondent deductions in
the Brunonian Elementa Medicina, a work (with some exceptions) of great
genius, must be considered as confirmations of the truth of the theory, as
they were probably arrived at by different trains of reasoning.

Thus in those who have been exposed to cold and hunger there is a
deficiency of stimulus. While in nervous fever there is a deficiency of
sensorial power. And in habitual drunkards, in a morning before their usual
potation, there is a deficiency both of stimulus and of sensorial power.
While, on the other hand, in the beginning of intoxication there is an
excess of stimulus; in the hot-ach, after the hands have been immersed in
snow, there is a redundancy of sensorial power; and in inflammatory
diseases with arterial strength, there is an excess of both.

Hence if the sensorial power be lessened, while the quantity of stimulus
remains the same as in nervous fever, the frequency of repetition of the
arterial contractions may continue, but their force in respect to removing
obstacles, as in promoting the circulation of the blood, or the velocity of
each contraction, will be diminished, that is, the animal strength will be
lessened. And secondly, if the quantity of sensorial power be lessened, and
the stimulus